Automatic positioning mechanism



April 28,, 1970 G. A. FISHER AUTOMATIC POSITIONING MECHANISM -2 Sheets-Sheet 1 Filed Nov. 1, 1968 l1\ LNTOR George 0. fisher BY ATTORNEY 2 Sheets-Sheet 2 Filed Nov. 1, 1968 [N VENTOR George 0. Fisher ATTORNEY United States Patent 3,508,675 AUTOMATIC POSITIONING MECHANISM George A. Fisher, Mentor, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Nov. 1, 1968, Ser. No. 772,482 Int. Cl. E02f 3/70 US. Cl. 214762 5 Claims ABSTRACT OF THE DISCLOSURE An automatic positioning mechanism for a front end loader vehicle having a pivoted lift arm movable by a hydraulic cylinder between a lowered-dig position and a raised-dump position. A valve controls flow of pressurized fluid to the hydraulic cylinder and is movable from a detented operating position to a closed position when a cam supported by the lift arm assumes a position related to a predetermined raised position of the lift arm.

Most shovelloading equipment presently manufactured is provided with a mechanism for automatically ositioning the lift arm when it assumes a predetermined position above the ground in order to relieve the operator from this task and thereby increase the efficiency of the loading operation. The present invention relates to a mechanism of this sort which is simple in design, inexpensive to manufacture and has adjustment features which permit the operator to quickly change the position where the lift arm is to be stopped. In its preferred form, the mechanism made in accordance with the invention includes a cam member that is supported by the vehicle for rotation about an axis coincidental with the support axis of the lift arm. An adjustment screw is pivotally connected at one end to the lift arm and has the other end threadably fastened to the cam member through a pivotal connection offset from the rotational axis of the cam member. By rotating a knob secured to the adjustment screw, the cam member can be located at a number of different points along a prescribed are about the lift arms support axis. Each position of the cam is related to a position of the lift arm so when the lift arm assumes a predetermined height, the cam member serves to deactivate the hydraulic circuit controlling movement of the lift arm.

The objects of the present invention are to provide a mechanism for automatically positioning the lift arm of a front end loader at a predetermined height; to provide a positioning mechanism located on and movable with the lift arm of a front end loader vehicle for automatically discontinuing flow of pressurized fluid to the lift cylinders when the lift arm attains a predetermined position; and to provide an automatic positioning mechanism for the lift arm of a loader vehicle that incorporates adjustable screw means readily accessible to the vehicle operator for quickly varying the height at which the lift arm is to stop upward or downward movement.

Other objects and advantages of the present invention will be more apparent from the following detailed description when taken with the drawings in which:

FIGURE 1 shows a front end loader vehicle incorporating an automatic positioning mechanism made in accordance with the invention;

FIGURE 2 is an enlarged view showing in detail the automatic positioning mechanism incorporated with the lift arms of the loader vehicle in FIGURE 1;

FIGURE 3 is an enlarged sectional view taken on line 33 of FIGURE 2, and

FIGURE 4 is a schematic diagram showing the automatic positioning mechanism of FIGURES 2 and 3 incorporated with a hydraulic control circuit which supplies pressurized fiuid to the lift cylinders.

Referring to the drawings and more specifically FIG- URE 1 thereof, a rubber-tired front end loader vehicle 10 is shown comprising a tractor 12 which is driven by the usual engine (not shown) located in the rear compartment area 14 of the vehicle. An operators station 16 is provided on the tractor 12 and has located adjacent thereto a control panel 18 including a lever 20 having three positions to be described hereinafter. The lever 20 serves to control movement of a hydraulic lift cylinder 22 pivotally connected between the front end of the tractor 12 and a lift arm 24. The lift arm 24 has one end thereof pivotally supported on the tractor 12 by a pivot pin 26 mounted in a support bracket 27 as to permit movement of the lift arm between a lowered-dig position and a raised-dump position shown respectively in phantom and full lines in FIGURE 1. The other end of the lift arm 24 pivotally supports a material handling bucket 28, the movement of which about its support axis is controlled through a tilt linkage comprising a tilt cylinder 30, reversing lever 32 and a link 34, all of which are pivotally interconnected between the tractor and bucket 28 in a manner so as to provide a distorted parallelogram linkage. At this juncture, it should be noted that although not shown, the bucket support structure and linkage shown in FIGURE 1 has identical and corresponding parts located on the other side of the vehicle.

As is well known to those skilled in the art, by expanding and contracting the tilt cylinder 30, the bucket 28 is movable between the dig position shown in phantom lines and a roll-back or carry position utilized for hauling material to a dumping site. Moreover, in cases where the load in the bucket 28 is to be dumped within the hopper of a truck, the lift arm 24 must be raised high enough to permit such dumping as shown in full lines. Thereafter, the tilt cylinder 30 is expanded to rotate the bucket 28 forwardly in a clockwise direction to dump the load. As should be apparent, the height of the hopper will determine the height at which the lift arm 24 is raised to permit the aforementioned dumping op eration, and inasmuch as it is difficult to estimate the proper height to which the bucket 28 should be raised to provide optimum dumping, it is important to have some form of automatic means to discontinue fluid flow to the lift cylinder .22 when the latter attains a predetermined length during expansion. Accordingly, an automatic positioning mechanism 36 made according to the invention fulfills this need as will now be described.

As shown in FIGURE 2, the lift arm 24 is supported on the tractor 12 by the support bracket 27 which is rigidly Welded to a frame member 40 secured to the tractor. A cam member 42 is rotatably supported by a bolt 44 which passes through a spacer 45 and is secured to the pivot pin 26. The longitudinal center axis of the bolt 44 is coincidental with the center of the pivot pin 26 which supports the lift arm 24 as aforedescribed. The cam member 42 has a riser portion 46 which is located in a predetermined position relative to the lift arm 24 and can be moved to other positions through an adjustment arrangement which comprises a clevis member 48, an adjustment screw 50 and a support member 52. As best seen in FIGURE 3, the adjustment screw 50 has one end thereof threadably received by a bore 54 formed in the clevis member 48 and the latter has its spaced legs connected to the cam member 42 at a point offset from the center axis of the bolt 44 by a pivot pin 56. The other end of the adjustment screw 50 freely extends through a passage or bore 58 in the support member 52 which is connected to the lift arm 24 by a bolt 60 secured to a spacer member 62 rigid with the lift arm 24. The bolt 60 serves as a pivot connection for the support member 52 for reasons which will become apparent as the description of the invention proceeds. A knob 64 is rigidly secured to the adjustment screw and serves as a means for rotating the latter so the clevis member 48 can be drawn toward or moved away from the support member 52 resulting in repositioning of the cam member 42 about bolt 44. A pair of nuts 66 and 68 threadably carried by the adjustment screw on opposite sides of the support member 52 serve as means for locking the adjustment screw 50 in position once adjustment of the cam member 42 has been completed. Thus, it should be apparent that in the position shown in FIGURES 2 and 3, the adjustment screw 50 is locked in position and in order to vary the position of the cam member 42, nut 66 must first be loosened thereby permitting the adjustment screw 50 to be rotated in a direction which would cause the clevis member to move either upwardly or downwardly along the shank of the adjustment screw 50. Thereafter, nut 66 will again be tightened against the lower end of the support member 52 to lock the screw against rotation which could be caused by vibrations or otherwise.

As shown in FIGURE 4, the automatic positioning mechanism 36 described above is incorporated with an operating circuit which controls movement of the lift cylinder 22 and includes a control valve 70 which is intended to be located within the control panel 18 and operated by the lever 20 referred to above. The control valve 70 includes a spool valve 72 biased by springs 76 and 78 toward a neutral closed position and having one end provided with an annular groove 79. The opposite end of the spool valve 72 has an ear 80 which is pivotally connected to the lever 20 and movable between positions indicated by the letters L, N, and R which respectively are the Lower position, Neutral position and Raise position. As is well known to those skilled in the art, when the spool valve 72 is located in the R position, a ball 82 biased upwardly by a spring -84 is adapted to move into the groove 79 and serve as a detent for holding the spool valve 72 in position at which time pressurized fiuid generated by a pump 86 flows through lines 87 and 88 to the base or cylinder end of the lift cylinder 22 to cause the latter to expand and raise the lift arm 24. During such time, the fluid at the piston rod end of the lift cylinder is vented to a reservoir 89 through lines 90 and 92.

When the lift arm 24 reaches a predetermined height, the cam member 42 is adapted to close a microswitch 94 by engaging a roller 96 supported by a plunger 98. The microswitch 94 is located on an angle iron 99 secured to the frame member 40 adjacent the positioning mechanism 36 as seen in FIGURE 2, and is a part of an electric circuit which includes a power source 100 and a solenoid operated valve 102 all of which are connected together in series by conductors 104, 106 and 108. Thus, when the roller 96 is engaged by portion 46 of the cam member 42, the coil in the valve 102 is energized causing the valve to shift in a position so as to connect a source of compressed air 110 via lines 112 and 114 with an actuator 116.

The actuator 116 is located adjacent the lever 20 and includes a piston 118 which is biased inwardly by a spring 120. The piston 118 has a rod which is adapted to move out of the actuator housing when the compressed air is connected with the latter. Thus, as shown in FIGURE 4, when the electric circuit is energized by the cam member 42, the air circuit including the actuator 116 is activated causing the piston 118 to be moved in an outward direction relative to the support housing and engage the lever 20. As a result, the lever rotates about its pivotal support 122 in a counterclockwise direction and frees the spool valve 72 from the holding action provided by the ball 82. The spool valve 72, being under the influence of the spring 76, then returns back to the neutral or closed position and thereby discontinues flow of pressurized fluid to the lift cylinder 22.

One of the features of the present invention is that Cir the automatic positioning mechanism 36 of FIGURES 2 and 3 is located externally of the lift arm 24 and is readily accessible by the vehicle operator. This permits the vehicle operator to quickly change the height at which the lift arm 24 is to be stopped by a simple operation requiring a minimum of tools. For example, a wrench will be adequate for loosening the nut 66. Thereafter, in order to obtain an automatic stopping of the lift arm 24 at a predetermined height, it is merely necessary to raise or lower the lift arm to the height desired after which the adjustment screw 50 is rotated so as to place the riser portion 46 of the cam member 42 in engageent with the roller 96. The nut 66 is then locked in engagement with the support member 52 and automatic positioning of the lift arm 24 is thereafter provided in a manner as described above.

Various changes and modifications can be made in this construction without departing from the spirit of the invention. Such changes and modifications are contemplated by the inventor and he does not wish to be limited except by the scope of the appended claims.

I claim:

1. An automatic positioning mechanism for a front end loader vehicle having a lift arm mounted thereon for pivotal movement about an axis transverse to the longitudinal axis of the vehicle, a bucket supported by said lift arm, a hydraulic cylinder for moving said lift arm and bucket between a lowered-dig position and a raised-dump position, a hydraulic circuit including a spring closed valve having a closed position and a detented operating position for supplying pressurized hydraulic fluid to said hydraulic cylinder to raise said lift arm, the improvement wherein said mechanism comprises a cam member supported on said vehicle for rotation about said transverse axis, a clevis member pivotally connected to said cam member at a point radially spaced from said transverse axis, the free end of the clevis member being formed with a bore, an adjustment screw having an intermediate portion thereof supported by the lift arm for movement therewith, one end of the adjustment screw being threadably received by said bore so that movement of the lift arm results in corresponding movement of the cam member about its support axis, a knob fixed to the other end of the adjustment screw for rotating the latter whereby said clevis member is moved along said screw to vary the position of said cam member about said transverse axis relative to the lift arm, an actuator located adjacent said valve for freeing the latter from the detented operating position, and means engageable by said cam member when the lift arm is raised by said hydraulic cylinder to a predetermined position and being operatively connected to said actuator and ada ted to activate the latter when the lift arm reaches said predetermined position.

2. An automatic positioning mechanism for a front end loader vehicle having a lift arm mounted thereon for pivotal movement about an axis transverse to the longitudinal axis of the vehicle, a double-acting hydraulic cylinder for moving said lift arm between a lowered-dig position and a raised-dump position, a hydraulic circuit including a spring closed valve having a closed position and a detented operating position for supplying pressurized hydraulic fluid to said hydraulic cylinder, the improvement wherein said mechanism comprises a cam member supported on said vehicle for rotation about said transverse axis, a clexis member pivotally connected to said cam member at a point radially spaced from said transverse axis, the free end of the clevis member being formed with a bore, a support member pivotally connected to the lift arm and having an open-ended passage formed therein, an adjustment screw having one end rotatably supported in said passage and the other end threadably received by said bore so that movement of the lift arm results in corresponding movement of the cam about its support axis, a knob fixed to said one end of the adjustment screw for rotating the latter whereby said cleavis member is moved along said screw to vary the position of said cam about said transverse axis relative to said lift arm, an actuator located adjacent said valve for freeing the latter from the detented operating position, and means engageable by said cam member when the lift arm is raised by said hydraulic cylinder to a predetermined position, said means being operatively connected to said actuator and adapted to activate the activator when the lift arm reaches said predetermined position.

3. The mechanism of claim 2 wherein said actuator is part of an air circuit including a solenoid operated air valve, and said means engageable by said cam member is an electric switch in series with said solenoid operated air valve.

4. The mechanism of claim 2 wherein a nut is threadably supported by the adjustment screw on each side of said support member for locking said adjustment screw from rotation.

5. An automatic positioning mechanism for a rubbertired front end loader vehicle having a lift arm, a pivotal connection mounting the rear of the lift arm on the vehicle for movement about an axis transverse to the longitudinal axis of the vehicle, a bucket supported by the front end of the lift arm, a double-acting hydraulic cylinder for moving said lift arm and bucket between a lowereddig position and a raised-dump position, a hydraulic circuit including a spring closed valve having a closed position and a detented operating position for supplying pressurized hydraulic fluid to the base end of said hydraulic cylinder to raise the lift arm, the improvement wherein said mechanism comprises a cam member supported on said pivotal connection for rotation about said transverse axis, said cam member having a raised portion adapted to follow a prescribed arc as the cam member rotates, a clevis member pivotally connected to said cam member at a point angularly spaced from said raised portion and radially spaced from said transverse axis, the free end of the clevis member being formed With a bore, a support member pivotally connected to the lift arm and having an open-ended passage formed therein, an adjustment screw having an intermediate portion rotatably supported in said passage and movable with the lift arm, one end of the adjustment screw threadably received by said bore so that movement of the lift arm results in corresponding movement of the cam member about its support axis, a knob fixed to said one end of the adjustment screw for rotating the latter to vary the position of said cam member about said transverse axis relative to the lift arm, an actuator located adjacent said valve for freeing the latter from the detented operating position, and means engageable by said raised portion of said cam member when the lift arm is raised by said hydraulic cylinder to a predetermined position, said means being operatively connected to said actuator and adapted to activate the actuator when the lift arm reaches said predetermined position.

References Cited UNITED STATES PATENTS 3,155,252 11/1964 Muellner et al. 214762 HUGO O. SCHULZ, Primary Examiner 

